Decorator Design Pattern: -
“Adding some extra class ,function or object to an original class without
changing its structure is called decorator pattern.”
It helps user to add some extra functionality in existing
class, this type of design pattern comes under structural pattern because it
behaves like a wrapper to existing class.
Decorator pattern is nothing but just decorating a class
adding some extra element in that class.
Consider a demo example shown below.in this the original class
is house consisting of walls, step, roof. Now we are decorating this house by adding
window doors, doors by using their respective classes.
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Code:-
#include<iostream>
using namespace std;
class House
{
public:
virtual void
draw() = 0;
virtual ~House()
{
}
};
class NormalHouse:public House
{
public:
void draw()
{
cout<<"Walls + Step + roof";
}
};
class HouseDecorator:public House
{
public:
HouseDecorator(House& dd):D_Decorator(dd)
{
}
void draw()
{
D_Decorator.draw();
}
private:
House&
D_Decorator;
};
class Door:public HouseDecorator
{
public:
Door(House&
dd):HouseDecorator(dd)
{
}
void draw()
{
HouseDecorator::draw();
cout<<"+Door";
}
};
class Windowdoor:public HouseDecorator
{
public:
Windowdoor(House& dd):HouseDecorator(dd)
{
}
void draw()
{
//HouseDecorator::draw();
cout<<"+Windowdoor"<<endl;
}
};
int main()
{
House* h=new
NormalHouse();
h->draw();
House* d= new
Door(*h);
d->draw();
House* w=new
Windowdoor(*d);
w->draw();
return 0;
}
Result:-
Nice concept....!!
ReplyDeleteGood work keep it up
ReplyDelete